Susceptibility of willows to oviposition by the willow sawfly, Nematus oligospilus

Abstract

Different combinations of shoots of 30 Salix species, clones or identified hybrids, were exposed to Nematus oligospilus to determine which were preferred for oviposition. Single N. oligospilus, enclosed in gauze cages, chose from 9-12 terminal shoots in which to oviposit. There was wide variation in fecundity (49.3±4.3 eggs/female; range 0-100). Sawflies oviposited in all tree-willows (subgenus Salix) screened-a selection dominated by clones of S. matsudana x S. alba hybrids, but wide variation in the number of eggs laid/shoot prevented a significant preference ranking. Shrub willows (subgenus Caprisalix) were, with one exception, not selected for oviposition.